The presence of a lump, or mass, on the gums can be indicative of several different conditions. It may be felt as a bump or hard or soft lump anywhere on the gums. An infection, such as a bacterial infection or localized abscess, can present as a mass on the gums. Oral cancers (gum or mouth cancer) or tumors of the teeth or jaw are rarer causes of a mass on the gums. A cyst of the jaw is also a possible cause of a lump or mass on the gums. Traumatic injuries and canker sores are some of the more common causes of a mass on the gums. Sometimes, the hormonal changes of pregnancy can cause a small lump or bump to form near the gum line, known as a pyogenic granuloma or granuloma gravidarum.